In a graphic display device for TV receiver etc., gamma-correction is the kind of correction to make both the input signal and the illuminating output signal of a display device become linear. Moreover, gamma-correction can also be carried out automatically based on the histogram and average brightness level of the graphic signals.
While carrying out gamma-correction, if the slope of the gamma-correction characteristic curve of the darker portion of graphic signals increases, the contrast of the darker portion will increase, and the noise component of graphic signals will also increase, causing even greater noise. From visual aspect, noise in the darker portion of graphic is more significant, thus in this case, more serious problems exist for graphic of poor signal-to-noise ratio such as significant noises.
Prior arts deal with such problems by restricting the amount of gamma-correction not to exceed certain specified value, which, however, is not an effective solution as far as noise is concerned.